Arc lamp



E. C. RICHARDSON ARC LAMP Filed sept. 27, 1933 May 2s, 193s.

Patented May 28, 1935 UNI-TED STATES PATENT OFFICE ARC LAMP ApplicationSeptember 27, 1933, Serial No. 691,143

2 Claims.

This invention relates to electric lamps of the character known as arclamps, and has particular reference to the type of arc lamps employingtwin or doubls arcs for illumination purposes.

5 In connection with certain industries requiring strong lighting, it iscommon practice to employ arc lamps as a source of illumination. One ofsuch industries is the motion picture industry in which a strong, steadylight is essential, and a common form of lamp employed in this industryis one known as The Twin Arc Lamp, consisting essentially in two sets ofcarbons arranged in close relation to each other and suitably connectedin electrical circuits so as to operate to draw two electric arcs.

The construction of twin arc lamps as now generally used consistsprimarily of a suitable pedestal or support upon which the lower orstationary carbons of each of the two sets of arcs are rigidly mounted,while the two movable carbons are mounted each upon its own separateyoke, and both yokes are connected to a single controlling magnet orsolenoid so that the actuation of the solenoid moves both sets ofcarbons simultaneously independent of whether or notV one of the carbonsrequires adjustment or movement.

It has been discovered that by separately controlling each of the setsof carbons constituting the arcs, the resultant illumination is greatlyincreased since each of the arcs may be drawn to its most eicient lengthindependent of the length of the twin or associated arc.

It is, therefore, an object of this invention to provide a twin arc lampin which the sets of carbons employed for producing each of the arcs isindividually controlled.

Another object of the invention is to provide a twin arc lamp in which acontrolling solenoid is provided for each of the sets of carbons.

Another object of the invention is to provide a twin arc lamp of thecharacter set forth in the preceding paragraph in which the controlling45 element of each arc comprises a solenoid having a current winding anda voltage Winding, the

current windings for the two arcs being connected in series relation,while the voltage winding for each of the solenoids is connected inparallel 50 relation to its individual set of carbons.

Other objects and advantages will be apparent from a study of thefollowing specifications, read in connection with the accompanyingdrawing, wherein 551 Figure 1 isa perspective view of a portion of anarc lamp structure illustrating the twin arcs and their controllingapparatus constructed in accordance with this invention; and

Figure 2 is a diagrammatic View illustrating the wiring connections forthe solenoids and the 5 carbons employed in the practice of thisinvention.

Referring to the drawing, there is illustrated a suitable supportingplate l which may be of any desired character, constituting a portion ofl0 the frame or mounting for the arc lamp structure. In illustrating theinvention herein, the cover for the controlling apparatus and thereilectors or casings employed for the complete makeup of the arc lampstructure, has been 15 omitted, though it will be understood by thoseskilled in the art that the mounting plate l will constitute a mountingplate for the carbons and their control apparatus, and that a suitablereflector may be employed for the purpose of pro- 20 jecting the lightfrom the arcs upon any desired position, and that any type of housingmay be built around the mechanism as may be desired.

The mounting plate I is illustrated as being constructed of insulatingmaterial, though it will also be understood by those skilled in the artthat the mounting plate may be composed of conducting material providingthe various pieces of apparatus mounted thereupon are electricallyinsulated therefrom. The mounting plate l is 30 illustrated as beingprovided with a pair of brackets 2 and 3 secured near the lower endthereof. The bracket 2, having an enlargement 4 upon its outer end,through which a suitable opening 5 may extend vertically for the recep-35 tion of the lower or stationary carbon G for one of the arcs, may befixed therein by means of a suitable wing bolt or set screw l, or otherclamping means.

The bracket 3 is illustrated as being provided with a suitable opening 8for the reception therein of the lower carbon 9 constituting thestationary carbon of the arc. Directly in vertical alignment with thebracket 2 is an upper bracket l0 constituting the support for the upperor movable carbon ll associated with the stationary carbon 6. The uppercarbon is preferably held in position upon the bracket I 0 by means of asuitable carbon feed clutch l2 which may be of any well-knownconstruction, such as that commonly employed in arc lamp practice asincluding a relatively flat plate having an opening therethroughsomewhat larger in diameter than the diameter of the carbon which isused so that by securing the rear end I3 of the clutch l2 to 55 anelevating mechanism, such as a lever lil, the lifting of the lever willcant the clutch to cause itto grip and lift the carbon Il. The lever Mis illustrated as being pivotally mounted as at l5 upon a suitablebearing i6 supported upon the bracket lil, the rear end il of the leverlil extending to the rear of the mounting plate i to permit theconnection thereto of a yoke it which is in turn connected to themagnetic core i9 of a suitable control solenoid 29, thel yoke i8 beinginsulated from the lever ifi by any of the various means known to theart.

The solenoid 2S is illustrated herein as comprising two separate coils,2i and 22, the coil 2i being formed of relatively heavy wire capable ofcarrying the current employed by the arc between the carbcns tand il,while the coil 22 is wound of relatively ne wire and has-its magneticpoles opposed to the magnetic poles of` the winding 2l. Thus byconnecting the coil 2i' `in series relation with the carbons S and ilany current owing through thecarbons will tend to draw the core -lS intothe solenoid and thus separate the carbone until the resistance acrossthe arose formed between the carbons reduces the current flowing inthecoil 2l and a state of balance is achieved. The coil 22 is connected inshunt relation with the carbonsv E and l l so that increase of potentialdrop across the are will permit an increased current'to flow through the'coil 22. With this type of control the algebraic sum of the pole ofthe'coil 2i on its core i9 and the magnetic balance of the coil 22negativing the magnetic force of thecoil 2l will balance the weight ofthe carbon i l when the carbone l l and E have been separated by Va lessdistance than if the coil 2l is used alone. Alsorthe effect of the coil22 is to retard the movement of the carbon il and thus cause thecarboni! to be'slowly drawn to the balanced position, thus slowlydrawing the arc and maintaining the arc at its most emcient length.

The electric values of the coils'Zi and 22 may be selected, as will beunderstood by those skilled in the art, 'to feed the carbons to thedesired arc length, though prefer to Yprovide an adjustment for the arclength which may consist of a suitable counterbalance 23 mounted upon anexpansion screw 24 secured rigidly to the lever Ill so thatby moving thecounterbalance Z toward the pivot l5, or away from the pivot l5, the arclength achieved by balance of the weight ofthe carbon with the magneticforces may be varied. The counterbalance 23 may also be adjusted tocompensate for changes in line voltage 'to insure that theintensity ofthe arc may be maintained constant, though the supply voltage may bematerially reduced or increased.

t has been discovered that if the current coil is constructedapproximately three times as long as the voltage coil and that if thecore i9 is constructed to be of a length slightly less Vthan the lengthof the current coil, a peculiarly desirable result is achieved in theoperation of the arc, namely, that the rapidity with which the arcs maybe struck and broughtto their normal feeding cycle is materiallylessened, and moreover the intensity of the illumination produced by thearcs during lthe period between the striking of the arc and the timethey are operatingon their normal feeding cycle is substantiallyconstant, thereby eliminating that initial period of theoperationn ofarc lamps during which the amountvof illumination produced variesbetweenV relatively great lengths. This is Vparticularly important in.A

the motion picture industry, as it is essential that the lamps beoperated' only during the time their illumination is actually requiredbecause photographic exposure is proportional to the light intensity andit is highly desirable to maintain a uniform light intensity during thephotographing period and because of the intense heat produced by manyarc lampson a motion picture set and yet the instant the illumination isrequired the full constant degree of illumination of the lamps isimmediately necessary.

Similarly the upper or movable carbon 25, constituting the movablecarbon associated with the stationary carbon 9 may be mounted upon abracket 2t through the agency of the suitable clutch?? identical withthe clutch l2, and connected in the same manner through a lever 28, theextending end 29 Yof which is connected to its own individual yoke 3% toits own individual controlling solenoid 3l, which solenoid, likesolenoid 2i3,iscomposed of a currentv coil- 32'and a voltage coil 33.rhe current coil 32Y of the solenoid'iV is connected in series relationnot only with its associated carbons 9 and 25, but also in seriesrelation with the coil 2li and carbon electrodes tiV and li, while thevoltage coil 33 is connected in shunt relation to its associated carbons9 and 25 to be affected solely by the length of arc drawn between thecarbons` il and 25.

By referring particularly to Figure 2 it will be observed that the `twinarc lamp constructed inaccordance with this Vinvention may utilize thecommonpractice of connecting the two arcs of the twin -arcs in seriesrelation as by supplying current from the positive terminal of asuitable source of electric supply', indicated by the sign plus, throughsuitable ballast-resistance Sdi to one terminalV of the coil 2l andthence from the other terminal of the coil 2l through a conductor 35 tothe movable carbon vil i thencethe circuit may continue through thearcfdrawn betweenV the carbon Il and the carbon 6, andV thence by.

way of conductor 35 to one end of the current coil 32 associated withVthe other set rof Vcarbons andY from the other terminal ofgthecoil 32to the movablev c'arbon' Vassociated with the carbon '9. The returnVcircuit `from the carbon 9 may becarried through a conductor 3l,ballastresistance to the negative side of thesource of powerindicated bytheminus sign. InFigure 2Y the connection of the voltage coil 22 is.illustrated as extending between` theconductor B and the conductor35'while similarly the voltage coil 33 is connectedY betweenconductorst'i and Slto, be in shunt relation with the carbons 25 and 9.

By referringrparticularly to Figure 2, Vit willV be noted that the twosolenoids A 2,!) and 31, as shown in `Figure 1, are mountedupon theplatefl in relatively close relation and have their axes parallel toeach other. Y

It has been discovered that by connecting the windings of the two coils`2| and 32 so 'thatthe polarity 'of the lower end ofV one of the coilsYis opposite lto the polarity-'of the lower end of the other coil, asubstantially closed magnetic circuitfisprovidedVV between the two coilsma-` teriallyfpreventing the magnetic eldf produced by either coil fromextending to and affecting -either of thearcs drawn between the sets ofcarbone. Thus by employing the two sets 'of carbons, e'achwith itsindividual solenoid, 'each'l setof carbone may be individuallycontrolled to` draw an arc of the greatest intensity and rgreat- Y est.ecieny. Moreover, ,the Muraille awayoigthe carbon of one set Will causeits particular feeding and controlling mechanism to operate withoutmaterially affecting the intensity or length of the arc drawn betweenthe other set of carbons. By employing the voltage coil and current coilopposing each other the burning away of one set of carbons will beaccompanied by an increase in the magnetic force of the voltage coil forthat carbon, opposing the current coil for that carbon, and will permitthe burning away carbon to feed down toward its stationary carbon tomaintain the arc length approximately constant until its clutch I2contacts with its bracket, at which time the clutch will release thecarbon, feeding the movable carbon toward the stationary carbon and/oradjusting the arc again to its proper length.

Such arrangement avoids the primary disadvantage of previouslyconstructed twin arc lamps in which a single feeding and controllingcoil was .employed for handling both movable carbons, since the burningaway of one carbon would cause movement of both carbons even though theother set of carbons had not burned at the same rate. Such operationprevented the arcs from operating at their maximum efficiency.

While the preferred embodiment of the invention is illustrated herein,it is not desired to be limited to any of the details shown or describedherein, except as defined in the appended claims.

I claim:

1. In a twin-arc lamp mechanism, a vertical supporting plate, a pair ofjuxtaposed brackets extending from the lower portion of said plate onone side thereof for supporting a pair of lower carbons, a pair of meansalso mounted on sai-d plate adjacent the upper end thereof forsupporting a pair of upper carbons above said lower carbons, each ofsaid means comprising a lever fulcrumed in front of said plate, means onthe forward end of said lever for supporting the associated uppercarbon, the rear end of each lever extending to the rear of said plateand having a downwardly extending magnetic core attached thereto, asolenoid surrounding each core and comprising a current coil connectedin series with the associated arc and a potential coil connected inshunt to the associated arc and poled to oppose the current coil of thatsolenoid, and a movable counterweight on each lever means for balancingthat lever and its associated carbon and magnetic core to compensate forvariations in the potential of the current from which the arc isenergized.

2. An arc mechanism as -described in claim 1 in which said solenoids arepositioned in substantially juxtaposed relation to their associated arcsand in juxtaposed relation to each other and in which the two solenoidsare so poled relative to each other that their magnetic fields are inlarge measure restricted to a closed path through the two solenoids,thereby reducing the stray eld in the vicinity of the said arcs.

ELMER C. RICHARDSON.

